The invention relates to wind generators used for producing electricity having propellers or blades that are rotated by the force of the wind to produce electrically. More specifically, the invention relates to bolt caps that are installed over the exposed top ends of the anchor bolts that secure the tower base to the foundation that is formed in the ground.
Presently there are numerous wind generators in existence that have a tower base 200 feet high or higher. These wind generators have blades or propellers up to 90 feet or longer. There may be as many as 240 or more anchor bolts used to secure the tower base to the foundation. The foundation itself may be in the order of 30 feet deep and these anchor bolts may also be in the order of 30 feet long. During the operation of anchoring the tower base to the foundation, a nut is tightened onto the top end of each of the anchor bolts. Next a second nut is threaded onto the top end of each of the anchor bolts. Then a hydraulic jack is used on each of the anchor bolts to stretch them by jacking them up with 70 to 80 thousand pounds of pre-stress tension and the first nuts are lightly tightened down. When the hydraulic pressure on the jack is released the prestressed anchor bolts tighten the nuts down against the annular flanges on the bottom end of the tower base. The top ends of the anchor bolts are now exposed to the elements such as sun, wind, rain, snow and moisture. Over time the moisture seeps down into the concrete around the anchor bolts in the foundation. This causes corrosion that weakens the anchor bolts and shortens the life of the tower base. Presently the wind generators and tower bases are amortized over about 20 years. By prevention corrosion to the anchor bolts, the life of the wind generator and its tower base can be extended several years. This is quite significant when it is kept in mind that a wind generator can cost a million or more dollars.
It is an object of the invention to provide a novel anchor bolt cap that can be used to cover the exposed top ends of anchor bolts used to secure the tower base of a wind generator to its foundation.
It is also an object of the invention to provide a novel anchor bolt cap that is designed to prevent it from rocking back and forth after it is installed on the top ends of anchor bolts used to secure the tower base of a wind generator to its foundation.
It is another object of the invention to provide a novel anchor bolt cap that has structure on the interior of its bottom end for centering and aligning the anchor bolt cap on a hexagonal nut that has been screwed onto the top end of the anchor bolts used to secure the tower base of a wind generator to its base foundation.
It is an additional object of the invention to provide a novel anchor bolt cap that is easily and quickly installed on the top ends of the anchor bolts used to secure the tower base of a wind generator to its base foundation.
It is a further object of the invention to provide a novel anchor bolt cap that is economical to manufacture and market.
Wind generators normally cost over a million dollars to manufacture and install them on an operational site. The base tower of the wind generators is often in the range of 200 feet high and the blades almost 100 feet long. The bottom ends of the tower base has to be secured to a substantial base foundation.
The base foundation is often in the order of 30 feet deep. The width of the base foundation is generally in the order of 10 to 15 feet in diameter. Approximately 250 anchor rods have their top ends extending upwardly from the top surface of the base foundation and they are spaced from each other in a circular pattern or a double circular pattern. These anchor rods have their bottom ends embedded in a tubular concrete structure that is formed on site.
The bottom end of the tower base has an outer annular flange and an inner annular flange and spaced apertures are formed in each of these around their periphery for mating with the respective top ends with the anchor bolts extending upwardly from the top surface of the base foundation. When the tower base is lowered onto the respective anchor bolts, they extend approximately ten inches above the top surface of the annular flanges on the bottom end of the tower base. A nut is threaded on the top end of each of the respective anchor bolts and snugged down against the top surface of the respective annular flanges. The reason for having approximately ten inches of the anchor bolts exposed is because a second nut is then threaded onto the xe2x80x9ctop endxe2x80x9d of the respective anchor bolts and a hydraulic jack is attached thereto for stretching and stressing the anchor bolts to approximately 70 to 80 thousand pounds of stress. Before removing the hydraulic jacks, the bottom nut is snugged against the top surface of the respective flanges.
The exposed outer surface of the top ends of the anchor bolts then has a film of grease applied thereto that cuts off any oxygen contact with the threads of the anchor bolts. At this time, the novel anchor bolt caps are slid over the top ends of the anchor bolts. The nut reception portion of the anchor bolt cap has interior structure that functions to align and center the anchor bolt cap over the top of the nut now resting adjacent the top surface of the respective annular flanges of the tower base. The interior of the nut reception portion has hexagonal shaped stepped wall portions that progressively have a reduced width as they extend further into the interior of the nut reception portion. When properly aligned and centered, the bolt cap is easily pounded down onto the top of the nut and frictionally held in place. The width of the interior of the anchor bolt reception portion is only slightly larger than the diameter of the anchor bolt. This eliminates the possibility of the anchor bolt cap being rocked back and forth either by the stresses produced upon it when the generator is operating or by individuals attempting to rock the anchor bolt caps off.